Is it a love letter from liberal Mormons to their church, or a Michael Moore-style hit piece on Mormon leaders?

The film 8: The Mormon Proposition, explores the role of the Church of Jesus Christ of Latter-day Saints in repealing same-sex marriage in California nearly two years ago. After debuting at last winter's Sundance Film Festival, the film opens in 15 cities nationwide today.

Director Reed Cowan had originally set out to document homeless and suicidal Mormon teens when another topic caught his attention.

In 2008, about six months after California's Supreme Court had struck down a ban on gay marriage, voters approved Proposition 8, a referendum that restricts marriage to heterosexual couples.

The LDS church's support for the referendum went all but unnoticed — for a time - until Mormons' significant deployment of moral and financial capital was discovered. Earlier this month, the LDS church agreed to pay a $5,500 fine for not reporting all of its nonmonetary contributions in support of Prop. 8.

Televised advertisements endorsed by the church urged the public to preserve traditional families. Church leaders warned that same-sex marriages ruin society and endanger souls and mobilized their congregations accordingly.

"Money, volunteers and a message. One organization with all three of these rose above the rest that summer, saying to the rest, 'Come follow me,' " says Dustin Lance Black, a narrator of the film. Black, known for penning the screenplay for the Oscar-winning film Milk, also writes for HBO's Big Love, which explores polygamy among modern fundamentalist Mormons not affiliated with the LDS church.

"I feel like this film in a lot of ways was my second mission," Greenstreet said. "I served a mission for the church - went out and pounded pavement and knocked on doors - so this is my second."

Mormon youth were taught how to persuade their friends and families to vote on Proposition 8, according to 8. Elder Quentin L. Cook, a Mormon leader, called on devotees to donate their "means and time" to the cause.

Critics of the film, including the Mormon church, said 8 takes a biased stance against the church.

"Clearly, anyone looking for balance and thoughtful discussion of a serious topic will need to look elsewhere," said Kim Farah, a LDS church spokesperson.